Japan launches ambitious robotic mission to Martian moon Phobos

What happened: Japan launched the $350 million Martian Moons Exploration mission, or MMX, to study Phobos and Deimos. The spacecraft will drop a small rover on Phobos and later collect soil samples for return to Earth. Key numbers: $350 million mission cost; launch at 3:41 p.m. Why it matters: The samples should determine whether the moons are captured asteroids or debris from a giant impact early in Mars' history. MMX would be the first spacecraft ever to return to Earth from the Mars system. Coverage: 6 outlets in 24h

Japan launched the $350 million Martian Moons Exploration mission, or MMX, to study Phobos and Deimos. The spacecraft will drop a small rover on Phobos and later collect soil samples for return to Earth.

The samples should determine whether the moons are captured asteroids or debris from a giant impact early in Mars' history. MMX would be the first spacecraft ever to return to Earth from the Mars system.